POU homeodomain proteins are transcription factors that play a role in differentiation, and the developmental control of neuroendocrine genes. The GnRH gene is expressed in a subset of hypothalamic neurons and is unique in its plasticity of its phenotype across development. GnRH neuronal phenotype is acquired rapidly as cells complete an early proliferation during embryogenesis, and then undergo loss and reinstatement during the estrous cycle. This led to the question whether POU proteins play a role in the control of neuronal GnRH gene expression. The POU-domain family members, SCIP and Brn-4 were cloned from GT1-7 neuronal cells. Physiological significance was shown by colocalization of SCIP or Brn-4 with GnRH in neurons in vivo. Overproduction of SCIP and Brn-4 was shown to repress or activate GnRH promoter activity, respectively, requiring both direct binding to DNA and protein-protein interactions. This proposal has 4 specific aims: Aim 1-To assess the expression of SCIP and Brn-4 in GnRH neurons in vivo; Aim 2-define the relevance of SCIP modulation of GnRH by targeted overexpression and antagonism of SCIP in transgenic animal; Aim 3-precisely localize the cis-acting elements of the GnRH promoter that mediate repression by SCIP and activation by Brn-4 and their protein partners; 4-identify and clone the protein partners that direct SCIP and Brn-4 action on GnRH. Together these studies will define the physiological role and cellular mechanisms of POU protein control and GnRH gene expression.